There has been known a production method in which a polyvinyl alcohol film is dyed with a dyeing liquid containing iodine and then stretched to obtain a polarizer (for example, JP-A-2003-270440). In the above-mentioned production method, the thus dyed and stretched film is subjected to an iodine ion impregnation treatment by immersing in an aqueous potassium iodide solution, and then subjected to an alcohol liquid immersion treatment by immersing in an alcohol liquid.
The polarizer obtained by this production method exhibits less yellowness and is less likely to cause a change in color hue even under a heating environment. The reason why the polarizer exhibits less yellowness is that absorbance thereof is nearly constant in the entire wavelength range of visible light.
However, the above-mentioned polarizer has a problem such as a low polarization degree.